Rotor arm and electrical system



Aug. 14, 1962 K. A. GRAHAM 3,049,643

ROTOR ARM AND ELECTRICAL SYSTEM Original Filed March 2, 1959 trilINVENTOR. Key/762% f7 674%4/77.

United States f it * fire 3,049,643 ROTOR ARM AND ELECTRICAL SYSTEMKenneth A. Graham, Birmingham, Mich, assignor to Chrysler Corporation,Highland Park, Mich., a corporation of Delaware Continuation ofapplication Ser. No. 796,530, Mar. 2,

1959. This application May 2, 1960, Ser. No. 26,373

4 Claims. (Cl. 315219) The present invention relates to internalcombustion engines and has particular reference to a new and improvedignition system therefor.

The present invention is an improvement over the ignition system ofPatent No. 2,819,428 and reference is also made to copending applicationof Omer E. Bowlus and Kenneth A. Graham, Serial No. 696,845, now PatentNo. 2,984,760, filed November 15, 1957, relating to a surface gap sparkplug which is described herein. This invention also relates toimprovements over the ignition system of copending application SerialNo. 796,448, filed March 2, 1959, of Orner E. Bowlus and Kenneth A.Graham, now abandoned.

This application is a continuation of my application Serial No. 796,530,now abandoned, entitled Rotor Arm and Electrical System, filed March 2,1959.

In the conventional ignition coil and magneto energized ignition systemsfor internal combustion engines wherein spark plugs are used having airgaps of a width within the range of 0.020 to 0.035 inch, the voltagesnecessary to electrically break down the air dielectric within theseplug gaps fall within the range of 4 to 25 thousand volts. The highvoltage spark is followed by a low current are of relatively longduration which is effective in igniting cold and/or lean fuel mixturesbut does not impinge upon carbon and lead fouling deposits whichpartially short the electrodes of these air gap plugs, nor contain theconcentrated energy required to raise the temperature of the spark to adegree suflicient to burn away these deposits on the insulator surfaceshould the spark actually contact these deposits by internal flash over.

The lack of concentrated energy in the spark is due in part to thecharacteristics of the ignition coil and magneto energy sources whichare characteristically slow in releasing their electrical energy. Theirslow release of energy is particularly disadvantageous to ignition whensufiicient plug fouling exist-s to drain or shunt to ground a relativelylarge portion of the total energy supplied to the plug. Should foulingdeposits of any substantial conductive capacity develop on the plugs thetotal energy dissipated by the shunting effect thereof may be sufiicientto prevent the voltage from building up high enough to initiate a sparkin the plug gaps.

Moreover, when using a conventional air gap plug of the type shown forexample in Patent No. 2,269,067 with these ignition coil or magnetoenergizing systems, the spark plug actually has little opportunity toburn away its own fouling deposits since the spark does not occur in theimmediate vicinity of these deposits which form on the insulator surfacebetween the base of the center electrode and the metal shell or groundelectrode of the plug. When these energizing systems on the other handare used with surface gap plugs where a spark can be effective inburning away fouling deposits, the rate of release of energy to theplugs is not sufiicient to burn away the fouling deposits and alsoperform its fuel ignition function.

A major object of this invention, therefore, is to provide a condenserdischarge ignition system with surface gap spark plugs to eliminatespark plug fouling by causing the spark to occur in the immediatevicinity of the fouling deposits and be sufiiciently hot to burn saiddeposits away.

A specific object is to provide a distributor rotor arm with a mainspark gap and a teaser gap in parallel so as to simplify the maintenanceand installation of these gaps in the ignition circuit.

Another specific object is to provide a distributor rotor arm withadjustable main spark and teaser gaps.

Another object is to provide an improved ignition system characterizedby its ability to produce a spark of sufficient duration and heat toinsure proper ignition of cold, lean and other combustion mixtures, andcombustion of the fouling deposits.

Another object of the invention is to provide an improved ignitionsystem which operates at a high frequency and low voltage compared toother systems known in the art.

A further object is to provide an ignition system capale of utilizingthe residual energy of the ignition coil after the plug fires tomaintain an arc having sufiicient heat to aid in burning away foulingdeposits and in igniting all fuel mixtures.

A still further object of the invention is to provide an improvedignition system which is characterized by its ease of operation and itsrelatively few number of parts.

Essentially the invention relates to an improved ignition systemutilizing conventional circuitry on the primary side of the ignitioncoil which delivers a relatively low frequency and low voltage power.The secondary circuit of the ignition coil is loaded by a secondary orignition condenser and is electrically connected in series to a rushtype distributor through the rotor arm thereof which is provided with amain spark gap and a teaser gap in parallel. The absence of rectifiersin the present system is particularly noted and the reasons therefor aredescribed below. The distributor is connected in the conentional mannerto a plurality of surface gap spark plugs generally of the typedisclosed in the aforementioned patent application and described below.By employing such a system the series main gap breaks down at apredetermined relatively low voltage and the charge which has been builtup on the secondary condenser discharges to the spark plug being firedto produce a spark of very short duration which is sufficiently hot toburn away fouling deposits. Moreover, the absence of rectifiers in thesystem allows the residual energy of the coil to be used to recharge thesecondary condenser to a progressively diminishing degree or continue anarc across the series gap and plug for a period of time sufficient toinsure complete fuel ignition. The resistor 48 helps prevent oscillatoryrecharging of the secondary condenser and allows continuous arcing. 'Iheionized condition of the series and spark plug gaps allows the flow ofcurrent in the secondary circuit to maintain the plug arc until theenergy decays to a level which will no longer support the arc.

Among the more significant advantages obtained by placing the main sparkgap or condenser discharge gap and the teaser gap in the rotor arm are:that a single metal distributor cap may be used to simultaneously shieldthe adjacent portions of the electrical system from the high frequencywaves emanating from the discharge gap and the teaser gap whichshielding results in a considerable cost saving and also reduced gapnoise; the accessibility of the rotor arm and gaps for installation,replacement, repair, and adjustment of the gaps; the movement of therotor arm resulting in air flow past the gap electrodes tending toremove shunting deposits of tungsten or other electrode metal oxidetherefrom; the location of the rotor arm which inherently subjects thesegap electrodes to breaker point vibration tending to dislodge foulingdeposits from the electrodes; and the necessary resistances for thecircuit can also be placed in the rotor arm in their proper circuitrelationship with respect to the gap electrodes for simplifiedinstallation and maintenance thereof.

Other objects and advantages of the invention will become apparent fromthe following description and drawings, in which:

FIGURE 1 is a schematic illustration of the electrical circuitry of theinvention;

FIGURE 2 is a top elevational view of the rotor arm;

FIGURE 3 is a cross sectional view of the rotor taken along line 33 ofFIGURE 2;

FIGURE 4 is a partial sectional view of the rotor taken along line 4-4of FIGURE 3;

FIGURE 5 is a side elevational View of a distributor;

FIGURE 6 is a cross sectional view of the distributor cap taken alongthe line 66 of FIGURE 5 in the direction of the arrows;

FIGURE 7 represents a cross sectional view of the surface gap sparkplug; and

FIGURE 8 represents a side view of a variation of rotor body structure.

Referring to the drawings and in particular to FIGURE 1, an ignitionsystem is shown comprising a direct current power source 10 such as abattery or dynamo which is connected to ground and to an ignition switch12 of the primary circuit 13. This switch is connected through avariable ballast resistor 14 to the primary winding 16 of a transformeror ignition coil 18. A pair of breaker switches 20 and 22 are connectedin parallel with a spark suppressing and primary voltage build-upcondenser 24 and are grounded at 26. Switches 20 and 22 represent theequivalent of the conventional breaker point contacts of ignitionsystems such as are shown in the aforementioned patent and arealternately opened and closed to produce a pulsating direct current inwinding 16. Condenser 24 prevents excessive sparking at switches 20 and22 and in series with winding 16 causes a high voltage oscillation inthe primary circuit.

The flux change linking both winding 16 and winding 28 and caused by thecollapse of the primary current when .the points 20 and 22 are openedinduces an oscillatory current flow in the secondary circuit 15comprised partially of the secondary winding 28 of coil 18 which on thefirst quarter wave of oscillation energized the secondary or ignitioncondenser 30 to a voltage of approximately 2-5 kilovolts. This condenserhas one plate connected to ground and the other plate connected to saidsecondary Winding and to a parallel arrangement of a main series sparkgap 32 and a teaser spark gap 34. Teaser gap 34 is almost continuouslyionized and tends to stabilize the voltage necessary to spark the maingap 32 at between 2,000 to 5,000 vol-ts. A resistance 35 is placed inthe teaser circuit to limit the current flow across this gap so as notto allow a significant discharge of the secondary condenser 30. Thecondenser 30 will charge up to the voltage necessary to spark series gap32 and spark plug gap 42 which results in a high current flow in thesecondary circuit to the plug.

As a result of this high current flow the are between the concentricelectrodes 44 and 46 of the surface gap plugs 42 is very hot and ismaintained for a very short time of approximately one microsecond. Thishot arc occurs directly across the face of the dielectric separator onwhich the fouling deposits occur and is particularly eifective inburning these fouling deposits from this face and also in igniting leanfuel mixtures.

Following the secondary condenser discharge is a low current aremaintained for approximately 250 microseconds by the residual energy ofthe coil 18. This residual energy is derived from continued oscillationof current in the primary circuit, while the points are opened, causedby the electrical resiliency of primary condenser 24 as it alternatelyattains charge and loses charge and also by the self-inductance ofprimary inductor winding 16. This low current are is especially suitablefor igniting certain cold and moisture laden fuel mixtures and continuesuntil the voltage induced by this residual energy cannot support thearc. By so utilizing this residual coil energy to supplement the energyof the condensers initial discharge the size of condenser 30 may be heldto a capacitance of approximately 1000 micromicrofarads which re-' ducescondenser cost and also reduces the degree of arc erosion of the plugelectrodes.

In order to prevent overly rapid dissipation of energy through the sparkplug, to help in igniting cold fuel mixtures, to aid in reducing radiointerference, and to help reduce electrode arc erosion, a resistance orinductance 48 may be placed in the circuit. This resistor or inductance48 also assists in maintaining the are at the spark plug after theinitial discharge of condenser 30-.

Plug 42 is disclosed in further detail in applicants copendingapplication Serial No. 696,845, and comprises an outer shell or groundelectrode 52 of conductive material which is swaged or otherwise formedover at the end 54 to retain the inserts 44, 46 of molybdenum or otherhigh temperature resistant metal and the dielectric insulator 45 whichmay be of porcelain or other insulative material known to the art. Acenter or power electrode 56 is spaced from the outer shell by insulator58 and is provided with a collar 60 which holds dielectric insert 45 inplace. Powdered insulator material 62 is compressed by the action of theassembly lock nut 64 to thereby properly position and maintain the plugparts in such position. As stated above, the voltage necessary toinitiate the spark in the plug gap is approximately 2,000 volts which isconsiderably less than that required to are a conventional air gap sparkplug.

Referring to FIGURES 3, 4, and 5, the rotor arm 66 to be used indistributor 68 is comprised of a body 70 of plastic or otherelectrically insulative material and is provided with a socket 72 forreceiving the rotor drive shaft 74 and a cavity 76 for housing the gapstructure. This cavity 76 could also be in the shape of a slot 77 acrossbody 70 as shown in FIGURE 8 formed by removing side walls 78 of body 70shown in FIGURE 4 to .allow increased air circulation in the vicinity ofthe gaps to assist in removing oxide deposits therefrom. Body 70 isprovided with two bores 80 and 82 which extend into cavity 76 andcommunicate with ledge 84 on one end of said body to form correspondinggrooves 81 and 83 therein. An electrically conductive tube 86 carrying atungsten or other high temperature resistant electrode cap 88 on one endthereof is slidably received in bore 82 and is adjustable longitudinallytherein. A resistor 35 having a tungsten or other high temperatureelectrode cap 92 on one terminal end 93 thereof and a metal tube 94swaged over on one end and soldered at 96 to the other terminal end 97of said resistor is slidably received in bore 80 and is adjustablelongitudinally therein. An electrically conductive clamping plate 98 ismounted on ledge 84 and contacts tube 86 and tube 94 to provide anelectrical path therebetween. Power lead spring contact 108 adapted tocontact the power inlet terminal 102 in the distributor cap 104 shown inFIGURE 6 is secured to plate 98 by bolt 106 and nut 108 which maintainsa firm electrical connection between spring contact 188 and electrodecaps 88 and 92.

An electrically conductive strip 110 is non-adjustably secured to body70 by a bolt 111 and nut 112 and is formed into a cross bar 114 at oneend which extends into cavity 76. Tungsten or other high temperatureresistant electrode caps 116 and 118 are secured to cross bar 1114. Tube86 and resistor 35 may be adjusted in their bores to properly space caps88 and 116 and 82 and 118 respectively to thereby form the main spark orcondenser discharge gap 32 and the teaser gap 34. Strip 110 is formed atits other end into a brush retaining hearing or socket 120 whichslidably receives a graphitecopper brush 122 which is urged in onedirection by a spring 124 secured to body 70 by nut 112. Brush 122 isadapted to slidably engage the conductive segments 126 on thedistributor cap 104 to complete at each contact of said segments anelectrical circuit from the secondary winding 28 and condenser 30through the spark plugs 42 which are connected through leads 128 to thesegments 126. In the operation of this system, as brush 122 wipes acrosseach of the segments 126 the condenser 39%) discharges across gap 32through the lead 128 and plug 42 connected thereto.

1 claim:

1. In an operative ignition circuit for a multiple cylinder engine, adistributor having an inlet terminal and a plurality of outletterminals, a plurality of surface gap spark plugs connected with saidoutlet terminals respectively, said distributor also having a rotatablearm, brush means carried by said arm and arranged to contact each ofsaid outlet terminals successively upon rotation of said arm, spark gapmeans carried by said arm and requiring a predetermined comparativelyhigh breakdown potential to initiate conduction of electric current andbeing thereafter susceptible of conducting at a lower conductingpotential until the latter potential is subjected to a predeterminedinterruption, one side of said gap means being electrically connectedwith said inlet terminal, the other side of said gap means beingelectrically connected with said brush means, a storage condenserelectrically connected with said inlet terminal to discharge throughsaid plug and gap means when the latter is conducting, electrical powersupply means for charging said condenser to said breakdown potential toeffect a sudden current surge through said gap means and plug upon thedischarge of said condenser, and resistance means for retarding the rateof discharge of said condenser sufficiently as the potential of thelatter approaches said conducting potential to prevent saidpredetermined interruption of said conducting potential by dampingoscillation of said condenser potential, said power supply means beingelfective to supply electrical power to said gap means at saidconducting potential for an extensive time interval with respect to theduration of said current surge to eilect a trailing current of extensiveduration across said gap means and plug following said current surge.

2. The combination according to claim 1 wherein said gap means includesa main gap having a fixed and an adjustable electrode mounted on saidarm at opposite sides of said gap means to enable adjustment of the gapbetween said electrodes, said gap means also including a teaser gaphaving a fixed and an adjustable electrode mounted on said arm atopposite sides of said gap means in parallelism with said main gap toenable adjustment of the gap between the latter electrodes.

3. The combination according to claim 1 wherein said resistance meansinterconnects said condenser and inlet terminal.

4. The combination according to claim 3 wherein said power supply meansincludes a battery, a transformer having primary windings connected withsaid battery to be energized thereby and also having secondary windingsconnected with said condenser to charge the same, and a condenser andbreaker point in an operative oscillator circuit with said primarywindings for interrupting the energizing thereof to effect a condensercharging potential across said secondary windings.

References Cited in the file of this patent UNITED STATES PATENTS791,856 Apple June 6, 1905 2,589,164 Tognola Mar. 11, 1952 2,819,428Bowlus et a1. Jan. 7, 1958 2,833,963 Tognola May 6, 1958

